The hollow center of the drum has force fed plastic explosive being pushed in Playdoh Fun Factory style.

A pellet of P.E. is extruded out a hole in the side of the drum, into a chamber with electrodes for detonation.

The explosion happens
as a notched section of the drum passes, then an exhaust hole. Repeat. A knifey object in another hole cuts out any residue to an even level. Repeat. Revs could be reduced by braking the drum, and/or firing every 2nd turn for example. The wheels are driven from a gearbox between the drum to the wheels.

You also haven't addressed how you will fire the PE. I think it requires an electrical firing charge. I always heard it was shock resistant and could be lit on fire with no ill effect. It is only dangerous when the blasting cap is connected to it.

To repeat myself, you need to put a blasting cap in each charge of C-4 to set it off. You can run an electric arc through in, or set it on fire, or hit it with a hammer and it isn't going to explode. You need to use a smaller explosion to set it off.

I'm still unclear on how a curved notch in a drum creates rotary motion. What you have described sounds more like a rotating pressure vessel to vent the excess pressure. There is no apparent compression or displacement change mechanism to translate the pressure into motion. Even with very very small portions I think you will have to make this an extremely large drum to with stand the pressure.

Not only incredibly expensive... but I'm thinking it wouldn't work. Plastic explosives such as C4 have incredible detonation velocities - as such, the blast effect isn't much for pushing. It's more of a shattering effect. Why do you think they use gun powder in bullets, rather than the more powerful flash powder? It'd just blow apart the cylinder...

I would make the steel thick enough to contain the explosion. If for some reason steel can not be made thick enough, then I will say poo poo to that because it can always be made thick enough to contain and convert the energy to rational energy.

"I would make the steel thick enough to contain the explosion. If for some reason steel can not be made thick enough, then I will say poo poo to that because it can always be made thick enough to contain and convert the energy to rational energy."

I don't think that you understand what I'm trying to say. It certainly is possible to make the steel thick enough to contain the explosion. However, it still won't drive. Plastic explosives explode too fast to actually propell anything. The blast isn't long enough. You'd need to use some sort of lower power fuel.